2-Trifluoroacetylthiopyridine–1-hydroxybenzotriazole: a powerful reagent for peptide synthesis

Abstract
A mixture of trifluoroacetylthiopyridine, the sodium salt of 1-hydroxybenzotriazole, and an acylamino acid is able to acylate amino acid esters in high yields with minimal racemization and should, therefore, be useful for fragment condensation reactions in the liquid phase.